1. Technical Field
The present invention relates to artificial knee joints, and more particularly, to an artificial knee joint that has a natural flexion movement of the knee in which the amount of rollback of a femoral component is small in slight flexion of the knee joint, and large in deep flexion thereof.
2. Background Art
When the knee joint is deformed seriously due to a degenerative knee joint disease or chronic rheumatism, a replacement surgery of an artificial knee joint is performed to restore the normal function of the knee joint.
Various proposals are made about artificial knee joints to enable the natural movement of the knee even after the replacement of the artificial knee joint. An artificial knee joint is known which is less likely to be dislocated in slight flexion, but can rotate externally in deep flexion by way of example (see, for example, JP 2010-188051 A). In the artificial knee joint, the femoral component fixed to a distal end of a femur includes a medial condyle, a lateral condyle, an opening between the medial condyle and the lateral condyle, and an elliptical spherical sliding portion for coupling posterior ends of the medial and lateral condyles together. The elliptical spherical sliding portion is adapted to slide against a tibial plate in flexion of the knee joint. The tibial plate fixed to a proximal end of a tibia includes a medial fossa for accommodating the medial condyle, a lateral fossa for accommodating the lateral condyle, a spine to be inserted into the opening, and a concave sliding surface for forming a posterior surface of the spine and slidably accommodating the elliptical spherical sliding portion.